Siderophores are microbial iron transport compounds of low molecular weight, mostly water-soluble, that bind and solubilize the metal making it available for metabolic purposes. They afford a valuable natural products approach for the clinical treatment of iron overload, a condition that characterizes several pathological conditions. The proposed research deals with a) structural characterization of siderophores produced by the bacterium Pseudomonas fluorescens, b) studies on the effect of metal-binding on ferioxamine B (clinically) known as DesferalR), c) detection of secondary binding of divalent cations to ferrichrome siderophores, and d) investigation of conformational aspects of crambin, a small water-insoluble protein, as a model for membrane bound cellular siderophore receptors. Our approach makes extensive use of high resolution nuclear magnetic resonance spectroscopy on siderophore derivatives where the paramagnetic Fe(III) center is substituted by a convenient diamagnetic ion, such as Al3 plus. It is hoped that these studies will contribute to the design of drugs tailored for iron sequestration in humans.